In the search for oil and gas, operators have utilized various types of devices in order to drill wells. Operators are continually searching for ways to drill the wells faster and more economically. Traditionally, a specifically designed drill string was used to drill wells. The drill string would have attached thereto a drill bit. In order to drill the well, the driller would cause the drill string to rotate which would in turn cause the bit to rotate, and hence, drill the well. Over the years, various types of drill strings have been developed in order to drill directional, or inclined, well bores.
Further, different types of bottom hole assemblies have also been developed in order to drill these wells. Thus, a typical directional drill string may contain a bottom hole assembly which includes: a bit, bent sub, drilling motor, and measurement-while-drilling surveying and logging tools. With this type of bottom hole assembly, the drill string ideally is held stationary with respect to down hole rotation. The drilling motor generates rotation of the bit via circulation of the drilling fluid through the drilling motor as is well understood by those of ordinary skill in the art. With the drill string held stationary with respect to rotation, the well is drilled in the desired, controlled direction of the bend in the bent sub.
A common problem with this type of drilling assembly is the torque generated by the bit. The bit torque generates an equal and opposite reactive torque that is transferred from the motor into the bottom hole assembly and drill string, causing it to counter-rotate, relative to the bit. Further, the reactive torque, and hence the drill sting counter-rotation, varies due to drilling conditions, such as the weight applied to the bit, properties of the rock being drilled, and hole condition, which all vary independently of each other. As the bent sub is part of the bottom hole assembly being counter-rotated, the direction in which the well is being drilled changes with the changes in reactive torque.
As a result, the directional driller is required to make numerous surface adjustments of the drill string, and hence the bent sub, to maintain drilling in the desired direction. These numerous adjustments cost valuable rig time and reduce the efficiency of the drilling operation. By eliminating, or greatly reducing, the reactive torque in the bottom hole assembly and drill string, drilling can proceed unabated in the desired direction, saving valuable rig time. Other benefits of eliminating, or reducing, reactive torque include the ability to use more powerful motors and more weight on bit to increase drilling rates and drilling a smoother, less tortuous borehole for running logging tools and setting casing. A non-reactive bit apparatus and method were disclosed in U.S. Pat. No. 5,845,721 entitled “Drilling Device And Method Of Drilling Wells”, which is incorporated herein by express reference.
As those of ordinary skill in the art will appreciate, daily rig cost are substantial. In many cases after a well is drilled, the well is prepared for running and cementing a casing string into the well. Hence, any time saved cleaning, running and cementing the casing converts to significant cost savings. Prior art tools have not allowed an operator to effectively drill with a casing string forming a part of the work string due to structural limitations of the casing string and the casing string thread connections. In other words, the casing strings and casing string connections are not structurally designed to handle the stress and strain applied by the numerous torquing requirements for a drill string. However, with the advent of the non-reactive torque drilling device herein described, drilling with an attached casing string is possible. Numerous advantages and features flow from the non-reactive torque drilling device.
Therefore, there is a need for a drilling device that will allow the drilling of a well with a casing string attached thereto. There is also a need for a non-reactive drilling tool with dual bits, and wherein the casing string is left within the well after cessation of drilling operations. Under this scenario, the casing string can be cemented in place and other remedial well work can be performed, wherein the remedial well work includes perforating the casing in order to produce hydrocarbon from a subterranean reservoir.